No abstract

Interest in commercially viable cellulosic biofuel production has greatly increased due to concerns regarding the sustainability of petroleum fuels. While research into solving the technical issues surrounding cellulosic biofuels is ongoing, much less attention has been paid to solving supply chain challenges such as low bulk density of cellulosic biomass, compositional variability and seasonality of the feedstock, food vs fuel issues, and local environmental concerns. To address these supply chain problems, we explore the concept of Regional Biomass Processing Depots (RBPDs), strategically distributed facilities that procure, pre-process /pre-treat and densify biomass into stable intermediate products that are compatible with existing bulk commodity logistical systems. In this perspective, we discuss the fundamental concept of RBPDs, their functionality, advantages, and potential challenges. We then extend the analysis of depots to include enhanced confi gurations and discuss some technologies that might be deployed in RBPD networks and the valuable coproducts that might be produced via synergies among these technologies. Current biomass supply system: problems and some prospective solutionsB iofuels are a near-term opportunity for the United States and the rest of the world to reduce or eliminate our reliance on petroleum for transportation. Currently, grain ethanol and oilseed biodiesel represent only a small fraction of US transportation use, but the addition of cellulosic biofuels could greatly increase this fraction. Th e Energy Independence and Security Act of 2007, for example, mandates the production of 16 billion gallons of cellulosic ethanol by 2022. A shift from petroleum-based fuels to biofuels would be a tremendous undertaking, requiring hundreds of billions in investment and large shift s in land use. Such a shift , however, would produce substantial benefi ts in 622

There is an intense ongoing debate regarding the potential scale of biofuel production without creating adverse effects on food supply. We explore the possibility of three land-efficient technologies for producing food (actually animal feed), including leaf protein concentrates, pretreated forages, and double crops to increase the total amount of plant biomass available for biofuels. Using less than 30% of total U.S. cropland, pasture, and range, 400 billion liters of ethanol can be produced annually without decreasing domestic food production or agricultural exports. This approach also reduces U.S. greenhouse gas emissions by 670 Tg CO 2 -equivalent per year, or over 10% of total U.S. annual emissions, while increasing soil fertility and promoting biodiversity. Thus we can replace a large fraction of U.S. petroleum consumption without indirect land use change.